Effects of different screen mesh and cylinder models on the performance of Y-type screen filter

Y-type mesh filters have been widely used in the micro-irrigation systems. A better hydraulic performance is highly required for the stable operation during irrigation. In this study, the standard k-model was adopted to simulate the internal flow field of different filters using the computational fluid dynamics with multi-angle analysis. A series of simulation tests were carried out under three types of filter screen shapes (square, circular and diamond) and three angles of cylinder arc (0°, 15°, and 30°). Specifically, a systematic analysis was implemented on the hydraulic characteristics of the internal pressure drop coefficient, the flow distribution on the surface of the filter element, the internal flow field, and the pressure distribution. Physical tests were also conducted to verify the numerical simulation. The results show that: There was 9% average difference in the head loss coefficient between the physical test and the numerical simulation, indicating the better reliability of the numerical simulation. The head loss of the filter was concentrated on the outlet side of the screen, which was accounted for 85% of the total head loss. A stagnant zone of water flow was formed inside the plug, where the velocity was very low without the water flowing back. The smallest pressure was found in the center of the filter chamber from the center to the surrounding area. There was also an increase in the minimal pressure in a stepwise manner from the center to the periphery. Among them, the circular mesh filter shared the largest head loss coefficient, followed by the square mesh filter, and the smallest was found in the diamond mesh filter. The pressure dropped at the mesh, and the total pressure dropped to change, as the shape of the mesh changed. But there was no variation in the value and distribution of the maximum and minimum pressure in the chamber. It infers that the shape of the mesh posed a greater influence on the distribution of the overflow rate on the mesh surface of the filter. The highest proportion of medium-rate overflow area was 47.5% in the square mesh filters, followed by the circular shape, and the smallest medium-rate overflow area of diamond shape was only 26.5%. The head loss of the filter gradually decreased with the increase of the arc angle of the cartridge. The pressure drop coefficient at 35° decreased by 73.15%, compared with 0°. There was also the much more uniform distribution of the flow rate on the mesh surface with the increase of the angle, in which the area of the medium speed overflow area at 35° increased by 71.48%, compared with 0°, indicating the outstandingly improved hydraulic performance. There was the significant decrease in the internal and external pressure difference at the middle and upper section of the screen on the outlet side with the increase of the arc angle of the cartridge , particularly for the differences between 35° and 0°. The difference of the pressure drop between 35° and 0° was 2.97 times. Therefore, an optimal filter can be selected with a square cylinder arc angle of 30°in the actual micro-irrigation system, in order to improve the hydraulic performance and service life of the filter with the gentle internal flow field and uniform flow distribution on the mesh surface.